diff --git a/Python/ast_unparse.c b/Python/ast_unparse.c
index f376e86..1a7cd23 100644
--- a/Python/ast_unparse.c
+++ b/Python/ast_unparse.c
@@ -746,6 +746,7 @@
         APPEND_STR_IF(i > 0, ", ");
         APPEND(slice, (slice_ty)asdl_seq_GET(slice->v.ExtSlice.dims, i));
     }
+    APPEND_STR_IF(dims_count == 1, ",");
     return 0;
 }